Integrated circuit (IC) devices can include transistors, such as insulated gate field effect transistors (hereinafter referred to as MOS type transistors, but not implying any particular gate or gate insulator material). MOS type transistors can include gates, drains, sources and bodies. In some IC devices, or some circuits within an IC device, the bodies of transistors have a permanent connection to a power supply voltage. For example, bodies of p-channel MOS transistors are connected to a high power supply voltage (e.g., VDD), while bodies of n-channel transistors are connected to a low power supply voltage (e.g., VSS).
However, in other IC devices or circuits within an IC device, the bodies of transistors can be biased to potential different from a power supply voltage. Such body biasing can advantageously alter the performance of the transistors. For example, a greater reverse body bias (i.e., p-channels body biased to a voltage above VDD or n-channel body biased to a voltage less than VSS) can decrease a transistor current leakage. Greater forward body bias (i.e., p-channels body biased to a voltage below VDD or n-channel body biased to a voltage above VSS) can increase transistor switching speed. In some cases, an IC device can include one or more body bias voltage generating circuits to generate desired body bias voltages, which are then applied to the bodies of target transistors.
A drawback to implementing body biasing circuits can be the need to strictly control body voltages during the transient state of powering up the IC device. If body voltages levels are not strictly controlled, a p-n junction formed by a transistor body can forward bias, drawing a large amount of current, and possibly damaging the IC device. Further, the initial floating states of transistor bodies can give rise to latch-up conditions (activation of a parasitic bipolar junction transistor).